The present invention relates to an ink jet printer, which is capable of continuously jetting an ink and controlling a jet course thereof so as to stick the ink on a member to be printed for printing.
A general basic structure of a conventional continuous-jet type ink jet printer is shown in FIG. 17. An ink is supplied from an ink tank 109 and pressurized by a pump 108. The pressurized ink is formed into particles by supersonic vibration, which is caused by a piezoid 107, so that the ink particles 102 are continuously jetted from a nozzle 101. The ink particles are electrically charged by charging electrodes 103 and their jet courses are controlled by deflecting electrodes 104 to dispose them onto a face of a paper. To form the ink particles, the piezoid is usually employed as a means for applying supersonic vibration to the pressurized ink. Note that, numeral 105 stands for a gutter for collecting the ink, which is not used for printing, and numeral 106 stands for the paper.
The ink jet printer shown in FIG. 17 having the piezoid, however, has a disadvantage of vibration noise and unstable jet pressure of the ink. Especially, in case of having a full-line printing head, which is capable of simultaneously printing characters or images in one printing line without scanning, a large piezoid whose width is almost the same as that of the paper is required, so that much greater noise will be produced and influence of the unstable jet pressure will be also greater. Thus, in the conventional ink jet printer, it is difficult to realize the full-line ink jet printer, and printing speed cannot be increased because a printing head must be reciprocatively scanned.
In the case of employing a bubble jet type full-line printing head, the noise problem can be solved but durability of a heating body will be lower because the heating body must be large in the wide printing head, further, reliability of generating an ink bubble will be lower.
In case of employing a mach type printing head with the piezoid, which forms the ink particle one by one, to realize the full-line type printing head, performance of nozzles are scattered so reliability of jetting the ink will be lower.
Even in case of employing the full-line type printing head, the conventional ink jet printer must stop conveying the paper to print line by line, so printing time cannot be made shorter. The merit of the full-line printing head cannot be effected. Namely, it is required to print by the full-line type printing head without stopping conveying the paper.
In the full-line type printing head, it is necessary to control the jet course of the ink particles, which are continuously formed, so as to correctly print characters or images. But an increase of manufacturing cost must be limited.
It is required to smoothly supply the ink to the printing head; to smoothly collect and circulate the ink not used for reuse; to increase an amount of the ink circulating in the printing head; and to perfectly seal a housing in which the printing head is accommodated so as not to leak the ink. And it is also necessary to prevent the ink in the housing from drying while the ink jet printer is not used.
If the charging electrodes 103 and the deflecting electrodes 104 are made of rigid plates, inner faces of the housing must be formed to correspond to the shapes of the electrodes 103 and 104; otherwise positions to which the electrodes 103 and 104 are attached are limited, and it limits design of the printing head. This disadvantage is marked in case of the full-line printing head.
When the pressure of the ink changes, the jet course of the ink particles is unstable, so that characters of images printed on the paper will be distorted in the direction of the printing line.